Radio Frequency Identification (RFID) means are widely employed in present day systems. The biggest advantage of the RFID technology is that they are capable of reading RF tags from a long distance without requiring line of sight. The RF signals can penetrate through solid objects such as wood, glass, concrete and almost everything except metals and liquids. This feature of RF signals enables the use of RFID readers for reading assets through cabinets, racks and packaging materials. The penetration feature of RFID over a long range makes the inventory process quicker and more efficient.
RFID readers are available in different forms today such as fixed readers, mobile readers, vehicle mount readers and so on. Most commonly used forms are fixed readers and mobile readers. Fixed readers have a fixed position and are located close to the inventory to be scanned. Fixed readers are employed for reading one or more inventories that are located close to each other. On the other hand, mobile readers are movable and may be carried to any desired location for performing the scan. Using a mobile reader it is possible to scan all the inventories that are located in a particular area of interest.
However, the RFID readers have their own limitations. The range of RFID readers cannot be limited to within a particular area of interest. For example, when performing inventory of a building, the user may employ mobile RFID reader. Using the RFID reader the user may scan and record the assets that are present in each room. All the RFID tags that are scanned in the room become associated with the room number where the user performed the scan. However, as the RFID reader can read through the wall, there is every possibility that the reader records assets from an area that is close to the room. The tags that are read from adjacent rooms are referred to as cross reads. Due to cross reads, a user will not have an accurate account of the assets or inventory in a desired location. Further, since it is difficult to have an account, it becomes even more difficult to keep track of assets moving in and out of an area.
The challenge in detecting cross reads using a single mobile RFID reader is taking into account the randomness of performing every scan. The user walks with the mobile RFID reader and waves the reader in the direction of assets to scan them. In every scan, the user might have scanned assets from different positions and from different angles, meaning that the read parameters (signal strength, read count) are randomly changing in every scan. Also, the fact that the physical position of the assets might have changed between scans makes it even more difficult to determine if an asset is physically present in the current location (normal read) or in a nearby location (cross read).
Present day mechanisms employ some methods for reducing cross reads. One of the solutions is to employ a metal barrier to prevent the RFID reader from reading beyond the designated boundary. The walls may be lined with aluminium sheets to create a zone such that the RF radiations cannot penetrate in this zone. However, one cannot guarantee that the protection will be effective. There is also the possibility of RF radiations still penetrating the metal barrier, depending on the efficacy of the barrier. More importantly, this will add to the overall cost as a major change in the infrastructure is required to install such barriers.
In another solution, the power of the RFID reader is reduced. This method only reduces the sensitivity and range of operation of the reader. But the method does not confine a read to a designated area. This means that the user could still get cross reads even after reducing the power. Further, reducing the sensitivity would lead to inefficient performance of the RFID readers and the user will have to move closer to the tags in order to perform a scan. This negates the advantage of using RFID readers.
Further, in some systems, which do not reduce or detect the cross reads, users are expected to manually identify cross read items and correct the inaccuracies in the cross reads. This process would be time consuming and cumbersome.